In wireless communications, the HetNets employ conventional Macro base stations (BS) with large coverage area while a number of small base stations (i.e. Pico base stations) can be deployed opportunistically within the coverage area of the Macro base station (See FIG. 1). A User Equipment (UE) may communicate with the BS via the downlink and uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the base station. On the downlink communication, a transmission from the BS may encounter interference due to transmissions from neighbor base stations or from other wireless radio frequency (RF) transmitters. As a consequence, such UEs may experience relatively low signal-to-interference-and-noise ratios (SINRs), and thus typically receive much lower data rates than UEs located nearer to the base station.
Generally, when the user enters the HetNet, it identifies the pair of Macro and Pico BSs with highest received power level and can determine the ratio of power levels of the Pico and Macro BSs. For example, let the ratio be denoted as γ. The user associates with the Pico BS if γ>Bias otherwise it associates with the Macro BS. The biased association controls the percentage of users associated with the Pico BSs. Since the Macro BS has significantly higher transmitter power compared to the Pico BS, it has higher coverage footprint. Choosing a bias value of less than 1 ensures that more the users are associated with the Pico BS thus enhancing its utility.
Currently, co-channel interference limits the capacity of conventional homogeneous cellular networks. In the downlink, since the UE is generally connected to the BS with the largest received power and the interference power received from any other BSs is less than the serving BS power. Therefore, the total interference power has a tamed distribution. As a result, interference causes an acceptable degradation in Spectral Efficiency (SE). The Pico BSs within the coverage area of Macro BSs can lead to mutual interference between the Macro and Pico BSs. Though the biased BS association controls the interference to some extent, the total interference contributed by the Macro and Pico BSs may lead to significantly lower cell edge performance. In spite of the increase in interference levels, the overall reduction in mean spectral efficiency (SE) of a Macro/Pico BSs are considered to be acceptable, since the overall capacity of the network scales linearly with the total number of BSs.
Thus, there is need in the art for improving the interference suppression by using coordinated SIMO/MIMO codes among plurality of base stations in the HetNets.
The above information is presented as background information only to help the reader to understand the present invention. Applicants have made no determination and make no assertion as to whether any of the above might be applicable as Prior Art with regard to the present application.